RENIN-EXPRESSING CELLS ARE ASSOCIATED WITH BRANCHING OF THE DEVELOPING KIDNEY VASCULATURE

To define the relationship between renal vascular development and reni n distribution during kidney ontogeny, the complete renal arterial toe of Sprague Dawley rats during fetal (20 d and postnatal (1 to 90 d) l ife was microdissected and immunostained for renin. A shift in renin d istribution from interlobar and arcuate arteries in the fetus to the a fferent arterioles in the adult was observed. In addition, seven types of renin distribution along the afferent arterioles were identified. In type I, renin was distributed continuously along the whole length o f the afferent vessel. This pattern was most frequently observed in th e fetus. In type II, lenin extended upstream from the glomerulus but d id not occupy the whole length of the arteriole. This type was relativ ely constant throughout postnatal life. In type III, renin was present as bands along the afferent vessel; it was most frequently observed i n the fetal and early perinatal periods. In type IV, renin was restric ted to the ''classical'' juxtaglomerular localization. It was the most frequent type observed in the adult rat. In type V, no renin was foun d in the arteriole. It was the second most frequent type observed in t he adult rat. In addition, two ''mixed'' patterns, type III/IV and typ e III/II, were occasionally observed. The distribution of renin-expres sing cells was spatially and temporally associated with the developmen t of blood vessels. Development of a new arterial branch was preceded by the appearance of renin-expressing cells at the point of branching. This was followed by an outpouching of the arterial wall that progres sively elongated to form a new arteriole. During this process, renin-e xpressing cells were distributed along the whole of the newly formed v essel. As the vessel matured, renin-expressing cells became restricted to the juxtaglomerular portion of the afferent arteriole. It is concl uded that throughout life and within each individual arterial tree, ex pression of renin is heterogeneous, following patterns that are unique for each developmental stage. Furthermore, the association of renin-e xpressing cells with branching of renal arterioles suggests a role for these cells in the development of the kidney vasculature.